Score:0

Multi Monitor issue - Main monitor goes black but still detected after switch

de flag

my desktop is connected to 3 monitors, A B C, in that order

  1. A is a 24" curved monitor [HDMI]
  2. B is a 27" MSI optix MAG274QRF [Displayport]
  3. C is a 24" flat monitor [HDMI]

Monitor A is also connected to a HDMI switcher that can swap it over to an external laptop.

Problem

This is the weird part, when i press the switcher to switch monitor A to my laptop, A switches fine but B goes black. It still seems to be on and detected (my mouse disappears when i shift over to that screen) but its fully black screened.

When i switch monitor A back, then B appears ok again.

I dont get it, what does switching A have to do with B??

Extra Info

  1. GPU: NVIDIA 3080GTX
  2. Ubuntu 21.10 kernel 5.13.0-28-generic
  3. NVIDIA 470 Driver
Score:1
vg flag

How each switch works is very specific.

Most likely when you switch to the laptop, the switch makes it look as if the monitor is "disconnected" from your PC

Hence now you have a different configuration (2 monitors plugged) and either your drivers are failing to handle this properly.

Or alternatively the switch makes it look as if a dummy monitor is connected to your PC. Hence you have a different configuration (3 monitors plugged, but one of them is a different model/resolution)

Either may see more info if you go into the Display properties to see the new configuration. In Xubuntu the app is called xfce4-display-settings. I don't know about GNOME.

Image of xfce4-display-settings for reference

It is also possible your problem gets solved after running xrandr --auto (note: it may also screw your current config by setting all monitors to "mirror"; xrandr has lots of options to set it the way you want)

de flag
You led me down the right path, i uploaded an answer. thanks!
Score:1
de flag

Solved it, with the base idea provided by Matias in the other answer

It seems when i switch monitor A over, the refresh rate of monitor B drops from 164hz to 60hz, and somehow that causes the entire monitor to stay black. Manually switching it back to 164hz fixed the problem (below).

enter image description here

mangohost

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